Dr. R. SelvakkumarPh.D., Associate Professor
Department of Livestock Production Management
Veterinary College and Research Institute
Veerapandi, Theni-625 534
Adverse climatic conditions are definitely a great problem in Livestock and Poultry Farming due to its direct effect on the performance of the animals and birds. In this, summer heat causes several detrimental effects starting from loss of production to mortality, which will eventually reduce the profitability of the farm. Heat stress interferes with the poultry comfort and suppresses its production performance and survivability. Reduction in egg size, egg-shell quality and egg production, body weight & hatchability are the initial effects of heat stress and mortality will result during extreme heat.
Poultry birds have some physiological mechanism to overcome the heat stress for some level but this will not be helpful during extreme heat beyond the tolerable level. Further, high temperatures coupled with high humidity have even more harmful effects on poultry. Heat stress interferes with the broiler’s comfort and suppresses productive efficiency, growth rate, feed conversion and live weight gain. In poultry production, heat stress can be described as acute or chronic. In broilers, growth rates, feed efficiency and carcass quality are negatively affected. In Layers, egg production and egg quality characters are negatively affected.
Thermoneutral zone for poultry is 18 to 22 degree centigrade, and within this range, they do not have to spend energy on maintaining constant body temperature. Heat stress results from unsuccessful thermoregulation mechanisms and is due to absorb or produce a higher quantity of heat that they can lose.
contributing factors for heat stress
Effect of heat stress in poultry is influenced by
A. environmental factors
- Thermal irradiation
- Air temperature
- Stocking density
B. Animal related factor
- Body weight
- Feather coverage
- Dehydration status
- Metabolic rate
- Thermoregulatory mechanisms
- Physiological state of the birds
Route of heat loss in poultry
Poultry birds are homeothermic in nature and attempt is made to achieve a stable body temperaturenearly independent of the environmental temperature.
Poultry birds are able to lose their excess body heat themselves via different ways during heat stressed condition like
- Radiation (Emission of heat as electromagnetic waves)
- Convection (Loss of heat through cool circulating air)
- Conduction (Loss of heat by direct contact with the cooler objects)
- Evaporation (Loss of heat by evaporation)
- Vasodilation (Loss of heat by increase the peripheral blood supply)
Further, the efficiency of heat loss through the above routes are even better by some managemental alteration in housing and feeding. So, an integrated approach is essential to save the poultry birds from the negative effect of summer heat stress.
Housing management during hot weather
Housing design, ventilation system, construction materials and site of location have an effect on the inside temperature of the house. Hence, while constructing the housing, almost care should be taken to maintain the temperature inside the poultry house. Circulating air is helpful to the heat stressed bird to emit their body heat than still air. Proper circulation air can be achieved by proper ventilation. Apart from the ventilation, artificial circulating provisions (Fan)also must to achieve this goal.
Increasing the air movement over a bird is the most effective method to increase heat removal from birds. Proper air movement will help in lowering the air temperature thereby increasing the sensible heat loss from the birds.
Temporary false roofing, sprinklers and fogger spray also workout to reduce the inside house temperature. Permanent shades by planting trees near the poultry house will definitely reduce the heat load inside the poultry house. Care must be taken while using sprinklers and fogger spray, because improper use will increase the humidity which will further worsen the heat stress.
Maintaining a lower stocking density during the summer than normal will give more floor space per bird and allow more heat to escape from underneath their bodies and from the litter.
Feeding and watering management
During summer, the consumption of feed by birds is reduced to avoid excess heat production through metabolism and this will result in reduced body weight, egg production, and shell quality, so a proper feeding strategy is required.
Feed is providing energy by generating heat through metabolism. But, production of heat during the hot time of the day will further increase the heat load of the birds. In this situation steps are to be taken in such a way to avoid heat production through digestion during the hot period of the day.
Withdrawing from feeding before the peak temperature, and feeding them once the peak temperature is declining will help to save the birds from excessive heat production during the hot time of the day. Feeding the birds during the night time by providing extra lighting during night will compensate for the reduced feed intake during the day time.
The reduced feed intake can be compensated by increasing the nutrient density.
Water intake is increased in the heat affected birds. Hence, a cool water supply throughout the day is a must. Increase the Watering space should be increased to increase the water intake. Overhead tanks and pipe systems should be examined to keep the water cool.
Loss of extreme amounts of CO2 through panting interferes with the calcium metabolism in affected birds. Thus, this will affect the egg shell quality. This can be managed by adding Vitamin C, Vitamin E and also provide H₂CO₃ to prevent the blood from becoming alkalotic.
Heat stress causes increased loss of several minerals due to panting, reduced feed and water intake etc. this can be compensated by adding necessary electrolyte with the drinking waste.
Vaccination of birds during the sunny days will further increase the stress of the heat stressed birds. Vaccination done during the cooler part of the day will reduce the vaccine related stress in birds.
Insulating the water pipeline directly exposed to sunlight with gunny cloths will be helpful to maintain the water cooler in the pipeline.
Other managemental practices
- Unnecessary handling of birds during the hot period of the day should be avoided, and if it is necessary, it can be done during the cooler part of the day.
- Transport of the birds should be done before the hottest day time. Placing empty crates between rows during loading will increase the ventilation during transport.
- Provide sufficient overhang (1 meter) to avoid the direct fall of sunlight into the poultry house.
- Providing exhaust fans on one side and pad cooling on another side will help bring down the temperature of the inside house.
Adopting proper management techniques during hot summer will help to combat heat stress in poultry birds and also helps to avoid the financial loss by keep the birds healthy and productive throughout the summer.